Ok, I thought that the second category having it's value and score not in the same order as the others was the issue.
I can hardly access my admin panel, but I manage to go in every section, except the categories one.
On my front page I have "Failed to lookup view "footer" in views directory" or Failed to lookup view "admin/footer" in views directory
When I check my log, I have the exact issue as @brieucswales (his screenshot).
I have tried, restarting and rebooting, nothing changes.
If I stay on the homepage or admin panel every 30 secondes, I have a refresh notification that keeps poping-up even if I have already refreshed the page.
Since drag and dropping that category was the last thing I did, I'm guessing that's the issue. Since when I log out, I can see all the categories on the homepage except the one that I drag and dropped.